raceconditions

A race condition is a behavior flaw that occurs when a system's outcome depends on the relative timing of uncontrollable events, such as the interleaving of operations on shared state by concurrent threads or processes. If execution order varies, the result may be nondeterministic or incorrect.

Race conditions commonly arise in concurrent programming, parallel algorithms, asynchronous I/O, and distributed systems where multiple actors access and modify shared data without proper synchronization. They often involve non-atomic sequences such as check-then-act patterns or read-modify-write sequences that are not protected.

For example, two threads increment a shared counter without a lock: each reads the same initial value, increments, and writes back, producing a final value that is smaller than expected.

Leading to data corruption, violated invariants, lost updates, stale reads, or corrupt file states; race outcomes depend on timing and may not be reproducible.

Mitigation includes synchronization (mutexes, locks, semaphores), atomic operations, memory barriers, thread-safe data structures, immutability, and using message passing or actor models to reduce shared state. In testing, race detectors, stress tests, and static analysis help identify races.

In distributed contexts, race conditions can involve clock skew, partial failures; strategies include consensus algorithms, distributed transactions, idempotent operations, and careful sequencing; some systems favor eventual consistency with well-defined retry semantics.